BRPI0711473A2 - method of treating crushed cellulosic fibrous material, and pulp - Google Patents

Abstract

METHOD OF TREATING CRUSHED CELLULOSIC FIBROUS MATERIAL, AND, PULP. a method is presented for pretreating fibrous material sprayed with sodium carbonate and then cooking the pretreated material in the presence of anthraquinone (AQ). The resulting pulp produced has a high yield, increased strength, and a better bleaching compared to the pulp produced by prior art methods. AQ may also be introduced in the carbonate pretreatment stage. The method may also include an acid pretreatment, producing even greater properties for the pulp produced.

Description

"METHOD OF TREATMENT OF GRIND CELLULOSTIC FIBER MATERIAL, AND, PULP" FIELD OF THE INVENTION

The present invention relates to a process for treating crushed cellulosic fibrous material, e.g. wood chips, with carbonate pretreatment prior to cooking the cellulosic material with a cooking chemical in the presence of anthraquinone ( AQ).

BACKGROUND OF THE INVENTION

In the art of chemical pulp production, cellulosic material such as wood chips is treated with pulp production chemicals to produce pulp for use in papermaking and other products. The use of caustic soda (i.e. sodium hydroxide [NaOH] as a chemical for pulp production), referred to as soda cooking, in both batch and continuous digesters is well known in the art. There are several advantages to soda cooking, including the ability to raise recovery boiler design pressure to improve recovery boiler efficiency and the elimination of sulfur in the process. Among other benefits, the elimination of sulfur in the cooking process allows the use of black liquor gasification systems. The use of black liquor gasification results in an increase in power generation that is many times greater than the energy generated using a sulfur based system.

A disadvantage of soda cooking includes a lower pulp yield (for both softwood and hardwood) than that obtained by kraft cooking, ie cooking using sodium hydroxide (NaOH) and sodium sulfide (Na2S). as chemicals for pulp production. However, the addition of anthraquinone (AQ) in soda cooking has been shown to improve pulp yield and thus make the pulp yield comparable with that of kraft cooking. However, even with the addition of AQ, the pulp from soda cooking processes has weaker strength and poorer pulp bleaching compared to kraft cooking.

However, there are also disadvantages with anthraquinone and soda (SAQ) cooking compared to kraft cooking. For example, SAQ cooking requires larger amounts of NaOH and is more difficult to bleach pulp produced from a SAQ pulp production process.

For example, the more NaOH required, the more required recaustification. As known in the art, sodium carbonate recaustification to regenerate NaOH is performed as shown in equations 1 and 2 below.

Na2CO3 + CaO + H2O -> 2NaOH + CaCO3 [1]

CaCO3 -> CaO + CO2 [2]

The volume of NaOH per ton of wood pulp required is higher for SAQ cooking compared to NaOH required for kraft cooking. This larger volume of NaOH required in SAQ cooking is needed to compensate for sodium sulfide present in kraft cooking that is not present in SAQ cooking. As is known in the art, sodium sulfide (Na2S) present in kraft cooking is hydrolyzed to NaSH and NaOH and therefore impacts the cooking of cellulosic material during kraft cooking. The volume of NaOH required in AQ cooking is around 20% to 40% higher than in kraft cooking. This increased need for NaOH results in a greater need to convert, or caustify, the sodium carbonate (Na2CO3) from the recovery boiler to NaOH used in the digester of other parts of the fiberline.

For example, when an active alkali (AA = NAOH + Na2S based on Na2O) of 16.0% Na2O and 30% sulfide capacity is used for kraft pulp production, 11.2% of AA comes from NaOH and 4.8% AA is Na2S. In kraft recovery, where all sulfur is recovered as Na2S, recaustification would be required for conversion to NaOH so that the desired 11.2% Na2O would be obtained from the new chips. Production of hardwood SAQ pulp requires approximately the same effective alkali (EA = NaOH + 1 / 2Na2S based on Na2O) as kraft pulp production. In the above example of kraft pulp production, EA was 13.6% Na 2 O and a similar amount of alkali would be required for SAQ pulp production, but all of it would come from NaOH.

Furthermore, it is well known that semi-celluloses are rapidly dissolved in pulp production with soda, kraft, and SAQ, and that a significant fraction of NaOH is consumed in the degradation of semi-celluloses in higher molecular weight (MW) products. low. These low MW organic products are difficult to recover from the pulp effluent, referred to in the art as "black liquor", and they do not have high calorific values. It is also known that the recovery furnace green liquor is mainly Na2COs when the SAQ process is used.

Hardwood pulps have been shown to be processed using "Lo-Solids" cooking methods (as described in U.S. Patent Nos. 5,489,363; 5,536,366; 5,547,012; and 5,620,562; 5,662. 775, 5,824,188; 5,849,150; 5,849,151; 6,086,712; and 6,132,556; 6,159,337; 6,280,568; 6,346,167 which are incorporated herein by reference in their entirety) and soda -AQ (SAQ) as the cooking chemical results in a pulp with better strength than that produced by conventional kraft cooking. In addition, pulp produced from rigid wood material processed using the Lo-Solids® soda-AQ cooking method as the cooking product can achieve better terminal clarity than conventional but not so soda-AQ. clear about the pulp produced by kraft cooking. Although the consumption of bleaching chemicals with Lo-Solids Soda-AQ is better than Soda-AQ for some final clarity, pulp still requires more bleaching chemicals than pulp produced by kraft cooking. .

For these and other reasons, kraft cooking (and its various sulfur-related problems) is the industry's prevalent pulp production process. However, we have found that by pre-treating the cellulosic material with a substantially sulfur-free carbonate solution (<1 g / liter total sulfur) and then practicing SAQ, the disadvantage of producing SAQ pulp can be overcome.

U.S. Patent No. No. 1,887,241 (incorporated herein by reference in its entirety) discusses the pretreatment, also referred to as preboiling, of a cellulosic material with sodium carbonate, followed by treatment of the resulting material with soda or kraft cooking. In the process disclosed in the '241 patent, wood chips that have been steam-treated may be subjected to the carbonate pretreatment stage at a temperature of about 330 ° Fahrenheit, that is, about 165 ° Celsius (C). According to the '241 patent, the pretreatment stage using sodium carbonate reduces the amount of NaOH required. For example, as disclosed in U.S. Patent No. 1,887,241, a 10% amount of sodium carbonate on wood is used, together with 15% NaOH, as compared to about 25% NaOH added to the conventional process. baking with soda. Although pretreatment with sodium carbonate at about 165 ° C is disclosed in the above-mentioned patent, the high temperature treatment disclosed in the '241 patent (published in 1932), for various reasons, has not been accepted in the manufacturing industry. pulp and is typically not practiced today. The treatment disclosed in the '241 patent also does not involve the use of an anthraquinone in any processing step.

Recent advantages in the pulp industry include methods for removing silica from cellulosic material using a solution containing sodium carbonate (see U.S. Application No. 2006/0225852, incorporated herein by reference in its entirety). The methods set forth in application 0225852 refer to almost 100% removal of silica contained in the cellulosic material, such removal occurring prior to processing the fibrous material using conventional methods.

Aspects of the present invention present a method for processing cellulosic material that overcomes the disadvantages and shortcomings of prior art methods. For example, some aspects of the present invention provide an avenue for minimizing or eliminating the presence of pulp mill sulfur while producing a commercially viable product - a pending long-term need that is required by the pulp industry. .

SUMMARY OF THE INVENTION

The present invention in its various aspects relates to the pretreatment of cellulosic material with carbonate, such as substantially sulfur-free sodium carbonate (Na2CO3) (<1 g / liter total sulfur), followed by the cooking of the pre-cellulosic material. -treated in the presence of a pulping chemical such as sodium hydroxide alone (ie the "soda" process), but also sodium hydroxide and sodium sulfide (ie the "kraft" process), or a combination of soda and kraft, and additionally at least one anthraquinone, ie anthraquinone or a substituted anthraquinone, such as 2-methyl anthraquinone. AQ may be added at any time during the process. For example, an AQ may be added at the pretreatment stage, the cooking stage, or even both the pretreatment stage and the cooking stage, as well as before or after each stage (the addition of AQ at the cooking stage). may be performed as described in US Patent No. 6,569,289, incorporated herein by reference in its entirety).

One aspect of the invention is a method for treating the milled cellulosic fibrous material according to: a) treating the cellulosic fibrous material with a carbonate-containing solution, such as a substantially sulfur-free carbonate-containing solution, to produce a preprocessed cellulosic material. treated; (b) treating the pretreated cellulosic material with a pulping chemical for a sufficient time and at a temperature sufficient to produce a cellulose pulp, wherein in at least one of (a) and (b) the fibrous material Cellulose is treated with at least one anthraquinone. In this method, the cellulosic fibrous material may be treated with an anthraquinone in a), b), or both a) and b). In one aspect, the carbonate containing solution may be composed of a sodium carbonate containing solution. In another aspect, the pulping chemical may be composed of sodium hydroxide. In addition, the active pulping chemical may substantially consist of sodium hydroxide.

An aspect of the above method include additional steps, prior to a), the crushed fibrous material may be c) treated with an acidic solution, and thereafter c), d) extracting at least part of the acidic solution from the cellulosic fibrous material. .

In another aspect, the method produces a pulp having a lower percentage of tailings and a higher percentage of sieved yield compared to the pulp produced where a) is not practiced.

One aspect of the invention may further include oxygen delignification treatment as well as at least one bleaching stage, wherein the method produces a cellulosic pulp having a clarity greater than 80% elrepho. When an oxygen delignification treatment is performed, the method may produce a pulp having a lower kappa number after the oxygen delignification treatment at a predetermined sieving yield compared to a pulp produced without practicing a). As is known in the art, the kappa number is used to define the degree of delignification. It refers to the value of the modified pulp permanganate test that has been corrected for 50% chemical consumption. The kappa number has the advantage of a linear relationship to lignin content over a wide range, for example, the kappa number χ 0.15% =% lignin in the pulp.

A further aspect of the present invention relates to a method for treating crushed cellulosic fibrous material by treating the cellulosic fibrous material with a carbonate-containing solution to produce a pretreated cellulosic material, the treatment of pre-treated cellulosic material. treated with a pulp producing chemical for a sufficient time and at a temperature sufficient to produce a cellulosic pulp and a liquid containing a spent pulping chemical, treating the liquid containing the pulping chemical spent for the production of a carbonate containing solution and from the spent pulping chemical, the use of the carbonate containing solution produced from the spent pulping chemical as the carbonate containing solution in a) of the method described above .

Another aspect of the invention includes a method for treating crushed cellulosic fibrous material composed of a) treating the cellulosic fibrous material with an acid solution, b) treating the cellulosic fibrous material with a carbonate-containing solution to produce a preprocessed cellulosic material. and (c) treating the pretreated cellulosic material with a sulfur-containing pulp-producing chemical for a sufficient time and at a temperature sufficient to produce a cellulose pulp, wherein at least one of b) and (c) Cellulosic fibrous material is treated with an anthraquinone. The sulfur-containing pulp chemical typically may contain sodium hydroxide and sodium sulfide.

Yet another aspect of the invention is composed of a pulp produced by one of the above methods, wherein the pulp has a higher yield than that produced by prior art methods. These and other aspects and advantages of the invention may be more fully understood in view of the following descriptions of the drawings.

BRIEF DESCRIPTION OF DRAWINGS

The present invention will be better understood from the detailed description given below and the accompanying drawings, which are presented for illustration purposes only, and therefore are not a limitation of the present invention and where:

Figure 1 is a schematic diagram of a pulp production process in accordance with aspects of the present invention.

Figure 2 is a schematic illustration of a chemical recovery system that may be used in aspects of the invention.

Figure 3 is a recorded comparison of the pulp sieving yield produced by the aspects of the present invention with the pulps produced by the prior art.

Figure 4 is a comparison of the light absorption coefficient values of pulps produced by aspects of the present invention with pulps produced by prior art.

Figure 5 is a schematic illustration of catalysis of lignin and carbohydrate reactions by anthraquinone augmented by aspects of the invention.

DETAILED DESCRIPTION OF THE INVENTION Applicant has found that treating crushed cellulosic fibrous material, such as wood chips, in a first pretreatment stage with a carbonate compound, for example substantially sulfur-free sodium carbonate, and then in a second stage pulp production, for example, soda pulp production in the presence of an anthraquinone (AQ is used to symbolize any anthraquinone), - a better pulp can be produced. Better pulp is also produced if the pulp is acid treated before the first pretreatment stage, followed by the production of kraft pulp in the presence of an anthraquinone. For example, the pulp produced may be characterized by increased pulp yield, increased bleaching capacity, increased strength and fewer tailings, among other beneficial properties.

In addition, by treating the chips with a carbonate-containing solution prior to treating the chips with a pulping chemical, the amount of pulping chemical required in the pulping process for a desired treatment may be reduced. This development could have a significant impact on attempts to reduce or eliminate the sulfur-containing pulp production chemicals, more especially sodium sulfide (Na2S) content. As mentioned above, non-sulfur-containing pulp production processes such as the soda process and the SAQ process had limited acceptance in the industry due to the relatively poor quality of the pulp produced compared to the sulfur-containing kraft process. In addition, typically the soda and SAQ processes require a larger amount of chemical to produce pulp, ie sodium hydroxide (NaOH) compared to the kraft process. As will be discussed below, aspects of the present invention overcome these limitations while producing an economically viable pulp. A further aspect of the present invention relates to a method for treating crushed cellulosic fibrous material which includes: treating the cellulosic fibrous material with a substantially sulfur-free carbonate-containing solution to produce a pretreated cellulosic material, treating the pretreated cellulosic material with a pulping chemical such as an alkaline pulping chemical for a sufficient time and at a temperature sufficient to produce a pulp pulp and a liquid containing a chemical spent pulp production, treating the liquid containing the spent pulp production chemical to produce a carbonate-containing solution from the spent pulp production chemical, and using the carbonate-containing solution produced from the spent pulp chemical. production of spent pulp as the carbonate-containing solution in (a) as described above in paragraph 16. The carbonate-containing solutions may contain sodium carbonate and are comprised of from about 1% to about 12% sodium carbonate as Na2Ü on the chips. The above method may also include oxygen delignification treatment.

In one aspect, treatment of the liquid containing the spent pulping chemical includes the concentration of the liquid sufficient to withstand combustion, burning of the concentrated liquid to produce a carbonate-containing melt, and the introduction of a liquid into the melt to produce the carbonate-containing solution from the spent pulp production chemical.

Another aspect of the invention includes a method of treating crushed cellulosic fibrous material composed of a) treating cellulosic fibrous material with an acidic solution, b) treating the cellulosic fibrous material with a carbonate containing solution such as sodium carbonate to produce a pretreated cellulosic material, and c) treating the pretreated cellulosic material with a pulping chemical for a sufficient time and at a temperature sufficient to produce a cellulosic pulp, wherein at least one of b) and c ), the cellulosic fibrous material is treated with an anthraquinone.

Using the processes and methods in accordance with aspects of the invention, surprising results were found in laboratory tests. These improvements include: a reduction in factor H in the cooking stage that is larger than expected (the total factor H from the first treatment stage plus factor H of cooking is less than factor H without the first cooking stage). carbonate treatment with the same kappa number; this is shown in tables 2 and 3 below; increased pulp yield; increased bleaching; increased strength; and less tailings). As known in the art and for the purposes of this application, factor H refers to a method for the expression of cooking time and temperature as a single variable for delignification.

Figure 1 is a schematic diagram of a pulp production process 10 using aspects of the present invention, in which the crushed cellulosic fibrous material 12, e.g. wood chips, is treated by a carbonate pretreatment stage 14. is a cooking or pulping stage 16. It will be appreciated by those skilled in the art that although the term "wood chips" is used to facilitate discussion of the invention, aspects of the invention are not limited to the treatment of chips, but may be used for the treatment of any form of shredded cellulosic fibrous material, including, but not limited to, hardwood chips, softwood chips, sawdust, recycled fibers, recycled paper, agricultural waste such as bagasse, and other fibrous cellulosic material .

As is typical in the art, prior to being introduced into process 10, the chips 12 may typically be conditioned for treatment, for example steam-treated, to humidify the chips, heat the chips, and remove as much air and other gases as possible. to increase the penetration of treatment solutions. Steam treatment of the chips 12 may be practiced, for example, in a horizontal steam treatment vessel or a Diamondback® steam treatment vessel, both provided by Andritz Inc. of Glens Falls, NY, prior to treatment. According to aspects of the invention, at carbonate treatment stage 14 (also referred to as stage c, pretreatment stage, or first stage) of treatment, the chips 12 are treated with carbonate containing solution 13, typically a carbonate solution. sodium carbonate, although potassium and magnesium carbonate solutions may also be used. In one aspect of the invention, this carbonate containing solution may be substantially sulfur free. One skilled in the art will appreciate that such absence of sulfur may not mean that there is no sulfur present in the carbonate solution in the absolute sense, but that the solution would be "substantially" sulfur free. After treatment in the first stage 14, the chips 12 are then treated in a second pulp production stage 16, i.e. a cooking stage, with the pulp production chemical 20 for a sufficient time and at a sufficient temperature. for the production of a cellulosic pulp 18. Pulp 18 may typically be sent for further treatment, for example for washing, bleaching, or sieving, among other conventional treatments. The carbonate containing solution 13 may be produced from a variety of sources including, but not limited to, commercially available carbonate and carbonate recovered from a related process, such as from a chemical recovery cycle (e.g., as illustrated and discussed). Figure 2 below).

According to aspects of the present invention, the carbonate containing solution 13 may have a concentration of from about 1% to about 12% carbonate (expressed as Na 2 O) on the wood. For example, the carbonate-containing solution may have a concentration of from about 2% to about 9% as Na2O on wood. The carbonate containing solution may typically be produced as an aqueous solution, i.e. a carbonate in water solution, although other compounds may be present. One skilled in the art will understand the use of the term "about" as describing a percentage of carbonate and will find that absolute measurements are difficult to take and the use of the term "about" when describing percentage of carbonate is ubiquitous in the art. 1 k mol Na2CO3 (106 kg) is equivalent to 1 k mol Na2O (62 kg). Other carbonates, such as potassium and magnesium, may be added with molar equivalence to Na 2 O. Carbonate treatment 14 is typically practiced at a temperature greater than 100 ° C, for example between about 120 ° C and about 200 ° C. In one aspect, carbonate treatment 14 may be practiced between about 120 ° C. ° C to about 170 ° C, for example, from about 120 ° C to about 150 ° C. One skilled in the art will understand the use of the term "about" to describe temperature ranges and find it difficult to have Absolute measurements are taken and the use of the term "about" when describing temperature is ubiquitous in the art. Such use of the term "about" is understood by one of ordinary skill in the art to define measuring ranges for any parameter of the treatment process throughout this presentation, including pressure, time, temperature, percentage of components used in the pulp production process. and other related measurements. At such temperatures, treatment 14 may typically be practiced at super atmospheric pressure of from about 50 psig to about 150 psig (6586 to 16,919 kPa man.). Pretreatment stage 14 is typically practiced for a time sufficient to produce at least some benefit to the resulting pulp produced in process 10. For example, pretreatment stage 14 may be practiced for at least 5 minutes, but may be practiced for about 15 minutes to about 6 hours, depending on the nature and supply, that is, the nature of the chips 12, but typically is practiced in about 15 minutes to about 120 minutes.

In one aspect of the invention, after pretreatment 14 and prior to pulp production stage 16, at least part of the liquid present may be removed or extracted from the chips 12 as indicated by 25. In one aspect, liquid 25 containing Extracted carbonate may be treated, for example, in a recovery system, disposed of, or alternatively reused. For example, in one aspect, the carbonate-containing liquid may be recirculated and reused as the carbonate source or supplement 13.

After the pretreatment stage 14, the carbonate pretreated chips 12 are then treated at the pulp production stage 16 with a chemical for pulp production for a sufficient time and at a temperature sufficient to produce a cellulosic pulp. 18. Although only one stage 16 is shown in Figure 1 according to one aspect of the invention, however, one or more stages of pulp production may be provided 16. According to one aspect of the invention the chemical for pulp production 20 used in pulp production stage 16 may be mainly sodium hydroxide (NaOH), that is, pulp production stage 16 may be a "soda" pulp production stage. In another aspect of the invention, the pulp producing chemical 20 may be composed of NaOH and sodium sulfide (Na2S), that is, the pulping stage may be a sulfate treatment or a kraft treatment. . When the pulp production stage is composed of a kraft pulp production stage, in one aspect, the carbonate treatment stage 13 may be preceded by an acid stage 22 (as discussed below). However, according to aspects of the present invention, pulp production from pretreated chips 12 is practiced at pulp production stage 16 in the presence of at least one anthraquinone (AQ).

In one aspect, pulp production from chips 12 in the presence of AQ may be performed as described in U.S. Patent No. 6,569,289 (the disclosure of which is incorporated herein in its entirety by reference). Applicant has found that pretreatment of carbonate chips 12, especially Na 2 CO 3 followed by SAQ pulp production, produces a pulp 18 having improved properties, for example improved yield, reduced lignin, and improved bleaching capacity compared to pulps. produced by the prior art treatments. For example, experiments performed by the applicant suggest that there may be some synergistic effects on the carbonate or carbonate-AQ treatment and pulping process of the present invention that are typically not predictable with prior art AQ treatments.

According to aspects of the present invention, at least one AQ, or derivatives thereof or equivalent, is introduced at pretreatment stage 14, pulp production stage 16, or both stages 14 and 16. In one aspect, AQ may be produced in its reduced form (ie a chemical commonly referred to as AHQ, see Figure 5). In one aspect, an aqueous solution of AQ may be introduced at the carbonate pretreatment stage 14 (as indicated by the dashed line 17 in Figure 1), for example, provided before, at the beginning, in the middle, near the end of the stage. 14 or some combination thereof. The concentration of aqueous AQ introduced during stage 14 may range from about 0.01 wt% to about 0.20 wt% of chips, but is typically between about 0.05 and about 0.10 wt%. Weight. For the purposes of this request, AQ may be added at any time during the pulp production process as described in figure 1.

In one aspect, AQ may be introduced at pulp production stage 16 (as indicated by line 21 in Figure 1), for example at the beginning, middle, near the end of the stage, or some combination thereof. The concentration of aqueous AQ introduced during pulp production stage 16 may range from about 0.01 wt.% To about 0.20 wt.% In the chips, but typically is from about 0.05 to about 0. , 1% by weight in the chips. In one aspect, AQ may be introduced at the carbonate treatment stage 14, and omitted from the pulp production stage 16; in another respect, AQ may be introduced at both carbonate 14 and pulp production stages 16.

According to aspects of the invention, when a first treatment stage 14 using a sodium carbonate solution as the carbonate containing solution, for example a sulfur-free carbonate solution, is followed by a second pulp production stage 16 using NaOH (for example, with a load of about 13% NaOH on wood) and AQ (ie a SAQ cooking stage), surprising results have been identified in laboratory tests. A 13% NaOH dose on wood corresponds to about 10% Na 2 O, i.e. 2 kg mol or 80 kg NaOH is equivalent to 1 mol mol or 62 kg Na 2 O. For example, in the laboratory test, when a first stage of carbonate treatment 14 is followed by a second stage of soda pulp production 16 (with 13% NaOH on wood) in the presence of AQ, the production of carbonate treatment. The pulp has significantly lower NaOH requirements and produced a pulp with a yield closer to that produced by the kraft pulp without increasing the tailings produced.

In another aspect of the invention, prior to pretreatment stage 14, the chips 12 may be treated with an acid solution 19 at an acid stage 22 (shown in phantom in figure 1). When kraft pulp production in the presence of AQ is the pulp production method used, acid pretreatment 22 may be followed by carbonate treatment 14. Any acid containing solution may be used for acid 19, but in a Preferably, acid 19 is preferably a non-sulfur-containing acid solution, for example an organic acid (such as acetic acid) or an inorganic acid (such as nitric or hydrofluoric acid). In one aspect, stage 22 may be practiced in the presence of a naturally occurring acid, that is, a naturally occurring wood acid. Acid solution 19 may be produced to produce an aqueous environment around the chips 12 having a pH of about 6 or below, for example having a pH of between about 4 and about 6. Acid treatment may be practiced in a temperature greater than 50 ° C, for example about 80 ° C to about 160 ° C. The acid treatment stage 22 is typically practiced for a time sufficient to produce at least some benefit from the resulting pulp produced in process 10. For example, the acid treatment stage 22 may be practiced for at least 5 minutes, but may be practiced from about 30 minutes to about 6h, and typically is practiced from about 30 minutes to about 90 minutes, depending on the nature of the supply, for example the pH of the chips 12. The amount of acid required may include any amount required for the production of the same effect as 2 to 6% acetic acid at 120 ° C.

As shown in Figure 1, in one aspect of the invention, after acid treatment 22 and prior to carbonate pretreatment 14, at least part of the liquid present after acid treatment 22 may be removed or extracted from chips 12, as indicated by extraction stage 23 (shown in phantom in figure 1). In one aspect, the extracted acid-containing liquid 23 may be treated, for example, in a recovery system, discarded, or reused. For example, in one aspect, the acid-containing liquid may be recirculated and reused as the source of or the acid supplement 19.

Acid treatment may be provided by the chips 12, for example, the acid at stage 22 may be an acid resulting from wood maturation (ie wood that has been stored for a sufficient period of time to produce a naturally occurring acidulated liquor). from the wood itself). In another aspect, the acid at stage 22 may be provided by a conventional acid hydrolysis process, for example a process used for the removal of metals and other contaminants from chips 12. Such a process is disclosed in U.S. Patent No. 5,338. 366 (the presentation of which is incorporated herein by reference in its entirety).

According to aspects of the invention, combining acid treatment stage 22 with carbonate pretreatment stage 14 and pulp production stage 16 having NaOH (soda) and AQ, or NaOH and Na2S (kraft ) and AQ, or a combination of soda and AQ and krafit and AQ, the chemical consumption (e.g., the amount of NaOH required) may be reduced and the resulting pulp bleaching capacity 18 increased. That is, the amount of bleaching chemical required to achieve the desired clarity may be reduced compared to prior art treatments. In some aspects of the invention, it is also possible to see improvements in pulp yield when using the acid treatment process 22 followed by carbonate treatment 14 followed by SAQ. An improvement in bleaching capacity is observed if pulp production stage 16 is the kraft process. The disadvantages of consuming chemicals in SAQ cooking can be analyzed by the carbonate treatment stage 14 and aspects of the invention may also improve oxygen bleaching ability and most likely by other electron transfer oxidants such as chlorine dioxide. also. The acid treatment stage 22 (A) may further improve the bleaching ability of both soda-AQ and kraft pulps, especially after an oxygen delignification stage (O). A green kraft liqueur (Na2COs + Na2S) may be used as the carbonate source 13 if the pulp production process 16 includes a kraft process.

Figure 2 is a schematic illustration of a chemical recovery system 100 that may be used in aspects of the invention. Chemical recovery system 100 includes a conventional recovery furnace or aerator 110 for burning concentrated spent cooking liquor 112, for example black liquor, to produce a chemical melt (not shown) containing sodium carbonate and sodium sulfide. (when black liquor is made up of kraft black liquor), among other black liquor combustion products known in the art. According to conventional practice, the carbonate containing the melt is dissolved in water in vessel 114, that is, the green liquor tank, to produce an aqueous solution (known as "green liquor") containing carbonate. In one aspect, the sulfide-containing green liquor may be used for the carbonate-containing solution when the pulp production stage is composed of kraft pulp production. The carbonate treatment with the green liquor may be preceded by an acid treatment (stage 22 of figure 1) prior to the production of kraft pulp. The vessel 114 may be a green liquor tank or other suitable vessel as is known in the art. In accordance with prior art practice, aqueous sodium carbonate in vessel 144 is typically sent for further processing 120, causticing, to regenerate NaOH to be used for cooking or bleaching, for example, for oxygen delignification. . According to aspects of the invention, the carbonate in the green liquor in the vessel 114 may be used as the sole carbonate source 13 for the pretreatment stage 14 described in figure 1.

The improvements and advantages produced by aspects of the present invention have been investigated by the applicant in batch laboratory treatment vessels, that is, batch laboratory digesters. The results of such a laboratory test are summarized in Table 1. Such vessels are commonly used for the development of batch and continuous digester processes. In the present invention, a continuous or batch digester may be used.

Table 1 summarizes the treatment conditions and results obtained for a series of laboratory tests using batch digesters. The present invention corresponds to tests 1, 3, and 4 in Table 1, where at least some sodium carbonate is supplied in a first stage treatment followed by a soda-AQ (SAQ) pulp production stage. Run number 2 is a reference test that corresponds to the conventional SAQ pulp production stage without any carbonate pretreatment and run number 5 is a reference test that corresponds to a conventional kraft cooking without AQ.

Table 1

Effect of carbonate pretreatment on pulp production with soda / AQ as evidenced by batch pulp production laboratory tests

<table> table see original document page 21 </column> </row> <table>

1 as Na2O over the chips 210% NaOH Na2O + 6% Na2O Na2CO3. The other SAQ is cooked only with 10% NaOH NaOH. The cooked kraft used 12% NaOH of NaOH. 3 percentage on the chips 4kappa number of sieved pulp

In these laboratory tests, 0.8 kg of sugar maple (Acer saccharum) chips (a hardwood) were placed in a laboratory digester. The carbonate pretreatment summarized in Table 1 was carried out at 65 ° C and 170 ° C using a dose of 4.0 - 6.0% Na2 COs as Na2O over the chips, ie 6.8 - 10.3%. of Na2COs. In runs 1, 3, and 4, carbonate pretreatment (CPC = carbonate before cooking) was followed by pulp production by soda-AQ with only 10% NaOH as the slivers. The initial testing strategy after carbonate pretreatment will depressurize the batch digester (ie "blowing the digester") and the condensation of the gases expelled by the carbonate stage (ie the effluent). NaOH and AQ were added to the condensate effluent and the effluent with NaOH and AQ was recharged to the digester with the chip sample. The digester was then heated back to pulp production temperature.

Table 1 includes the "H factor" for the pretreatment and cooking stages of the tests. As is known in the art, factor H normalizes alkaline delignification rates with the temperature of a treatment. Typically, the higher the factor H, the stricter the treatment. The H factor during the second warm-up is included in the total for SAQ cooking. Table 1 also shows the pH of the liquor in the digester after carbonate pretreatment and after soda-AQ treatment.

The benefits of the present invention are reflected in the "sieving yield", "tailings", and "Kappa number" data shown in Table 1. As is known in the art, sieving yield is the percentage of original chips present in the chips. pulped after treatment and after the pulp has been sieved to remove chips, fines, pins, etc. that have not been sufficiently pulped in the process, and other non-fibrous fragments. As is known in the art, a relatively high sieving yield is preferable. Tailings are an indication of how much of the original chips were not fully cooked by the process, for example as isolated by sieving. The less waste is produced, the less wood is discarded or re-treated. As is also known in the art, the kappa number produces a relative indication of the amount of undesirable lignin present in the resulting pulp. Typically, the higher the kappa number, the more lignin present in the pulp and more bleaching chemical is required to achieve a desired bleaching clarity. Therefore, a smaller kappa number is preferable.

The data in table 1 ratify the advantages of the present invention. The data produced in table 1 show that the method shown in figure 1 offers a dramatic improvement in conventional pulp production through soda-AQ. For example, as shown in table 1, tailings values are the clearest indication of the advantage of aspects of the present invention. According to Table 1, run number 4 - corresponding to carbonate pretreatment and AQ-soda pulp production - yields a value of 0.3 for tailings with a screening rate of 55.3%. In comparison, run number 2 - representing prior art SAQ pulp production - yields a value of 27.0% for tailings and a significantly lower sieving yield of 28.4%. This means that aspects of the present invention cook more chips more efficiently to produce a pulp while retaining a significant portion of the pulp, as evidenced by the high yield. That is, the less tailings, the more efficient the cooking process will be. The data in Table 1 also indicate that run number 2 (corresponding to the prior art SAQ process) produces a final SAQ pH lower than runs 1, 3, and 4 (representing aspects of the invention) even despite the use of NaOH. 10% Na2O on wood in all four cases. We have developed the theory that the lower pH of the prior art SAQ process is due to a stronger base NaOH5, competing with Na2CO3 in disposable carbohydrate degradation reactions. Na2CO3 remains in solution in the SAQ cooking process and is not a strong enough base to make alkaline rearrangements necessary for lignin depolymerization and solubilization. When Na2CO3 is added by itself in a pretreatment, reactive carbohydrates react with it because it is the only alkali present. Aspects of the present invention allow more NaOH to be added at stage 16 to force depolymerization or degradation of lignin and thus may produce a more effective pulp production process.

Baking without carbonate pretreatment has also been investigated in laboratory tests to produce a basis for comparison with aspects of the present invention. The results of these tests are summarized in Table 2. In these tests, a series of kraft and SAQ pulps were prepared from sugar maple chips without carbonate precooking. One of the kraft pulp production tests was done with a higher sulfide capacity and a less effective alkali (10% Na2O on NaOH chips and 5% Na2O on Na2S chips), see second line. This data kraft pulp production test (second row in table 2) produced a higher sieving yield (approximately 1.0% higher chip sieving yield) compared to an EA kraft test. higher, ie 12% Na2O over NaOH chips and 4% Na2O over Na2S chips (see first row of data in table 2). Both pulps had approximately the same unbleached kappa number (ie 17.4 and 17.8). However, pulp produced using a lower EA (ie 10% NaOH and 5% Na2S in the second row of table 2) appeared to be less responsive to oxygen delignification (O2) than pulp produced with higher EA (12% NaOH and 4% Na2S), as will be discussed below. The applicant understands that the difference in post-02 kappa numbers between these pulps was significant. As also shown in table 2, a series of SAQ tests were also performed. As shown, tests with varying 0.1% EA and AQ loads on the chips produced pulps having kappa numbers as low as 15.2 with relatively few tailings.

Table 2

Typical properties of control pulp treatment through previous kraft pulp and soda-AQ processes (ie without carbonate pretreatment)

<table> table see original document page 25 </column> </row> <table>

1 as Na2Ü on the splinters

2 90 minutes to temperature

3 percentage on splinters

4 kappa number of sieved pulp

5 experience repeated at a later date

6 0.1% AQ over the chips

Carbonate precooking according to one aspect of the invention has been investigated in laboratory tests. The results of these tests are summarized in Table 3. Table 3 presents the treatment conditions for carbonate chip pretreatment followed by a SAQ treatment (lanes 1-5) and a kraft treatment (lanes 6 and 7). The advantages of carbonate precooking according to aspects of the invention are evident by comparing the results shown in table 2 (prior art) to those shown in table 3. For example, if run 1 in table 3 is compared with conventional SAQ in table 2 (fifth row of table 2) can be seen that a 30 minute carbonate stage at 165 ° C ("condition Cl", see notes 2 and 3 at the foot of table 3) reduced the requirements for alkali at the SAQ stage from 14.0% (in table 2) to 10% (in table 3) as Na2O. A comparison of the produced kappa numbers shows that unbleached pulp produced with carbonate pretreatment had a slightly lower kappa number (18.4 vs. 19.3) while sieving yield produced with carbonate pretreatment. slightly higher (53.1% vs. 52.8%). If SAQ-carbonate according to aspects of the invention (eg run 5 in table 3) is compared with kraft carbonate (eg run 7 in table 3) it can be seen that a higher yield (1.0% on the chips) is obtained for carbonate-SAQ compared to carbonate-kraft treatment. Higher yield results in a more efficient process, and therefore higher sieving yield is desired.

Aspects of the present invention may also result in a reduction in factor H in the cooking stage that is larger than would be expected. When comparing the results as described in Table 2 with those in Table 3, it is evident that the factor H produced in the treatment performed without carbonate pretreatment is greater than the total factor H for carbonate pretreatment plus cooking up to the same kappa number. For example, the factor H for pulp that was not pretreated (lines 3 - 5 in table 2) was over 1600 for SAQ. The H-factor for the SAQ stage for the first two carbonate (Cl) pretreated pulps (runs 1-2 in table 3) was 1239, and the H-factor for the Cl stage was 358 for a total of 1597 for the combined treatments. with carbonate and SAQ. The resulting 18.4 kappa number pre-treated carbonate pulp (row 1 of Table 3) had an improved pulp sieved yield, an improved bleaching capacity, and resulted in a smaller amount of tailings than non-previously pulps. treated. Another comparison illustrating the benefits of aspects of the present invention can be found in figure 3 as discussed below.

Table 3

Effect of carbonate pretreatment on the production process of soda-AQ pulp and sugar maple chip kraft

<table> table see original document page 27 </column> </row> <table>

110% Na 2 O for 0 SAQ; 8.5% and 3.0% of NaOHe Na2S in kraft

3 Cl = 30 minutes at 165 ° C; C2 = 60 minutes, 4.0% NaiO on the chips for all races except race 4, where 5.0% was used.

4 AQ added to stage C instead of SAQ

5 only 9% of Na2O in SAQ

After the baking tests discussed above and summarized in Table 2 and Table 3, the cellulosic material was bleached. The bleaching sequence used in the laboratory test was an OD0EpD1 (where O is the alkaline O2 stage; D0 is chlorine dioxide delignification with a final pH of 2 - 3; Ep is alkaline extraction with sodium hydroxide and hydrogen peroxide. for incremental delignification; D] and a chlorine dioxide bleaching with a final pH of 3.4 - 4.5). The application of chlorine dioxide at stage D0 is based on the formula:% by weight of chlorine dioxide on pulp = 0.076 χ kappa number of O2 pulp. According to the laboratory test performed, the applicant found that the kappa number 21.5 pulp produced in the AQ-soda pulp test (ie the data in the fourth row of table 2) could be produced with 12, 5% Na 2 O; however, this pulp was more difficult to bleach than pulp produced when 14.0% Na2O was used (i.e. data in the fifth and sixth rows of table 2). The reduction in kappa number due to O2 is typically an indicator of ease of bleaching. According to aspects of the invention, the bleaching ability of a soda-AQ pulp is improved by carbonate pretreatment. It will be appreciated by those skilled in the art that although this specific bleaching sequence is used in this investigation, in accordance with aspects of the invention, any known bleaching process may be used, including bleaching processes that eliminate chlorinated compounds, that is, bleaching processes. Totally chlorine free (TCF) bleaching that eliminates elemental chlorine, that is, elemental chlorine free (ECF) bleaching processes.

Figure 3 presents a record of a comparison of sieving yield as a function of the kappa number of delignification after oxygen for aspects of the present invention and prior art. As shown, aspects of the invention produce a pulp that is more easily bleached compared to conventional prior art methods. As is known in the art, percent sieving yield is a ratio of the weight of pulp produced from the process to the weight of wood feed to the process after the pulp produced has been sieved to remove knots, waste and other undesirable materials. . High sieving yield is preferable. The kappa number of O2 refers to the lignin content of boiled and oxygen-delignified pulp. As is known in the art, a smaller kappa number is preferable. With reference to figures 3 and 4, the following notes were used: A = acid; C = carbonate pretreatment; Kr = kraft treatment; SAQ = treatment with anthraquinone soda. The designation ("M + N)" means that the treatment was performed at M% NaOH on wood as Na2O and N% Na2S on wood as Na2O. The methods of the present invention further include an oxygen delignification treatment resulting in a pulp having a lower kappa number after oxygen delignification treatment with a predetermined sieving yield compared to a pulp produced by the method without practicing a pre-stage 14. treatment.

As shown in Figure 3, a dramatic improvement for carbonate pretreated soda-AQ ("X" C-SAQ) compared to soda-AQ pulp without pretreatment ("A" SAQ). According to the results shown in Figure 3, the kappa number that was produced by carbonate pretreatment followed by baking AQ ("X" C-SAQ) with soda gives a kappa number after O2 less than the kappa number. for AQ-soda pulp without pretreatment ("" SAQ). For example, the kappa number O2 for C-SAQ ("X") is only above 8 kappa with a percentage of sieving yield above 52% and the kappa number 02 for SAQ ("A") is approximately 10 0.5 kappa with a comparable sieving yield of approximately 52.5%. That is, in comparable sifted yields, one aspect of the present invention has a lower kappa number compared to the prior art. Thus, carbonate treatment reduces the kappa number of (both unbleached and after O stage).

In these laboratory tests, the yield loss at all stages with oxygen was approximately 1.4 - 1.8% over the pulp. The slight differences in yield loss during O stages are insignificant when converted to a "percentage on chips" basis. Carbonate treatment or acid treatment followed by carbonate pretreatment (i.e., "AC pretreatment") did not improve the fiber yield of kraft pulp production. However, as shown in Figure 3, carbonate and acid + carbonate pretreatments ("X" C-SAQ and "*" AC_SAQ) clearly improved the yield of SAQ pulp production ("A"). That is, according to aspects of the invention, a higher sieve yield is produced compared to conventional SAQ pulp production methods. Figure 4 presents a record of a comparison of fully bleached pulps as a function of the oxygen delignification kappa number for aspects of the present and prior art. The ordinate in figure 4 is the light absorption coefficient (LAC) value for fully bleached pulp after bleaching OC0EpD1 and the abscissa is the kappa number after O2. An observation from Figure 4 reveals that conventional soda-AQ pulps ("▲") contain more color (ie, have higher LAC values) than kraft pulps ("closed diamond"). However, soda-AQ pulp after acid (A) and carbonate (C) pretreatments ("open triangle" and "open diamond") according to aspects of the invention have an equal or slightly lower color content. than kraft pulps without pretreatments.

Additional laboratory tests were performed to compare the properties of the bleached kraft, acid bleached carbonate kraft, and anthraquinone soda carbonate and acid bleached pulps. Various properties of the prior art bleached kraft pulp, carbonate acid (AC) kraft pulp according to one aspect of the invention and acid and carbonate (AC) -SAQ pulp according to one aspect of the invention from Sugar maple are documented in Table 4. As shown in Table 4, the AQ soda pulp pretreated with both acid and carbonate treatments showed improved yield. Sieving yields were higher for AC-SAQ, a value of 53.2, compared with a yield below 52 for both prior art kraft and AC kraft pulps. AC pretreatment increased the final clarity of kraft pulp from 91.0 to 92.6.

Table 4

Properties of the bleached pulp produced by the prior art kraft process and the kraft-AC pulp production processes is AC-SAQ according to the present invention.

<table> table see original document page 31 </column> </row> <table>

1% on the chips

2% Elrepho

3 light scattering coefficient = 40.8 m2 / kg for the three pulps

When cooking according to aspects of the invention as illustrated in Figure 1, at least part of the stage A (acid stage) effluent may be displaced, for example 50% to 75% of the total stage A effluent with the carbonate containing solution. In one aspect, at least part and possibly all of the carbonate stage effluent may be transferred with the chips into the SAQ stage or kraft. In the laboratory tests recorded so far, carbonate stage effluent was recovered after passage through a condenser. NaOH was introduced into the effluent as granules and the AQ powder was dissolved in the condensed effluent. The effluent containing carbonate and AQ was then returned to the laboratory digester for the SAQ stage. A solution of sodium sulfide and NaOH granules are added to the carbonate stage effluent in the case of kraft pulp production. For the purposes of this request, clarity is a percentage of elrepho.

The applicant assumes that the use of part or all of the carbonate stage effluent may be important for aspects of the invention, for example for the SAQ-carbonate process. We believe this may be because it is possible that the carbonate effluent may contain various low molecular weight carbohydrates with reducing end groups. Carbohydrate dissolution during the carbonate stage is estimated to be approximately 5% of the original (oven-dried) sliver mass. Applicant believes that random carbohydrate hydrolysis would be expected and it is possible to form a new terminal reducing group with each hydrolysis. Higher concentration of reducing terminal groups would reduce AQ at a greater rate to form AHQ (anthrahydroquinone), that is, the active delignification catalyst. The AQ / AHQ catalytic cycle is shown schematically in figure 5. When a solid phase reduction terminal group is also oxidized to carboxylic acid it becomes resistant to the alkaline detachment reaction that reduces carbohydrate molecular weight and reduces pulp yield. . The above hypothesis may explain why the carbonate stage improves pulp yield for SAQ pulp production but not for kraft pulp production. Oxidation of carboxylic acid reduction end groups is not known to be a significant (or even occurring) reaction in the kraft process, or the soda process without the addition of AQ.

To further confirm the benefits of aspects of the invention, additional laboratory research was performed on splinters from a mixture of woods. For example, a splinter mixture of approximately 60% eastern cottonwood (Populus deltoids), approximately 20% white birch (Betula papyeifera), and approximately 20% sugar maple was used. The results for prior art kraft pulp production, prior art Soda-AQ pulp production and pulp production according to aspects of the invention, that is, with acid and acid / carbonate pretreatments are given in Table 5. Acid pretreatment conditions were:

A1: 20 minutes at 150 ° C with 1.5% acetic acid on the chips and (final pH approximately 3.5); and

A2: 60 minutes at 120 ° C with 3.0% acetic acid (final pH 3.2). As indicated in Table 5, pretreatment A1 produced a soda-AQ pulp with a higher (i.e. "final") clarity (90.8) than kraft (89.9), but the yield of pulp was something smaller. The milder A2 pretreatment with SAQ-carbonate acid produced a higher pulp yield (54.2%) than both the kraft pulp and SAQ pulp production processes. The A2C-SAQ treatment also provided higher bleaching clarity (89.2) than SAQ pulp production (88.4) but less than kraft pulp production (89.9). In one aspect of the invention, we believe that the severity of the stage (A) with the acid may preferably be greater than the A2 treatment with an acid, but lower than the acid treatment Ai for this chip supply. As also indicated in Table 5, the rate of stress strength development after 2000 PFI refining revolutions, as indicated by the "stress index" for the production of kraft acid pulp (78.3) and for the production of acid-SAQ pulp (86.1) was lower than for kraft pulp production (94.4). However, SAQ-carbonate acid has the highest rate (i.e. 100.2), further emphasizing the benefits of aspects of the invention. Based on the results shown in table 5, it appears that a pulp with higher yield and probably more semi-celluloses required less refining. There were no significant differences in tensile-tear curves.

Table 5

Effect of acid and acid / carbonate pretreatments on the production of kraft pulp and soda-AQ from mixed rigid woods

<table> table see original document page 33 </column> </row> <table>

1EA = 10% Na 2 O; 14.0% for other cookings 2 Canadian Standard Stress Index and 2000 PFI Revolutions (Light Load) for O2 Delignified Pulps In addition, the milder carbonate stage conditions have been studied to fully understand the benefits of production carbonate-SAQ pulps and to further differentiate the current invention from previous research in 1 241 where there were no anthraquinones involved. The results of this investigation are summarized in Table 6. A chip supply consisting of 50% sugar maple, 40% eastern cottonwood and 10% birch was prepared. The carbonate treatment stages according to aspects of the invention were performed at 130 ° C and 140 ° C with 3.0 or 5.0% Na2 CO3 loading (as Na2O) in the wood over a period of 30 or 60 minutes In these tests it took 30-35 minutes to reach the maximum temperature. About 70% of the carbonate stage effluent was drained and disposed of after carbonate treatment. The carbonate effluent was replaced with distilled water when pulp production chemicals were added for SAQ or kraft cooking.

Table 6

Carbonate Al30 ° Cel40 ° C precooking effect

<table> table see original document page 34 </column> </row> <table>

1 final pH of stage C

2 S = SAQ; K = Kraft

3 percentage of chips

4 kappa number of sieved pulp; O2 value in parentheses

5 Na2CC> 3 applied as% Na2Ü to splinters

According to the result presented in Table 6, the best results were obtained with a carbonate-SAQ treatment having a 60 minute carbonate stage at 140 ° C with 3% Na2CO3 in the chips (such as Na20) (eg. see race 5). Run 5 pulp had a chip sieving yield of approximately 2.0% higher than run 8 (reference kraft cooking) and only a 1.7 kappa unit disadvantage after oxygen delignification as compared to run 8. When comparing the kraft pulp with the pretreatment (run 6) the carbonate-SAQ pulp (run 5) had a yield advantage of approximately 1.0% on the chips. This yield advantage translated into a profit increase of approximately $ 4 M / year for a typical chemical pulp mill.

In addition, the combined factor H for the carbonate (C) and soda-AQ stages in race 5 is 897 (81 +816) produced a pulp having approximately the same kappa number (23.1 vs. 22.6). , a higher yield (55.8 vs. 54.2) and fewer tailings (0.6 vs. 1.0) compared to the prior art SAQ pulp produced without pretreatment but with an H factor of 992 (run 9). Time spent in the carbonate stage may have a significant impact on the resulting pulp. In laboratory tests, the additional 30 minutes at the carbonate stage at a pH of approximately 8 (see run 4 vs. run 5) resulted in a 1.6 kappa unit advantage after delignification with soda-AQ and oxygen. In addition, the extra 30 minutes in the carbonate stage produced a higher sieve yield. Additionally, it is believed that more reducing end groups were generated in the extra 30 minutes spent in the carbonate stage and the longer overall cooking time converted more tailings into sieved fibers.

Aspects of the invention may be performed in equipment for batch cooking (such as, but not limited to conventional or SuperBatch® rapid displacement heating) or continuous (such as, but not limited to conventional soda, conventional kraft, LoSolids® cooking, EWMCC cooking). ®, ITC® and compact cooking) where pressurized equipment (as required for carbonate treatment) is used for any or all stages of acid, carbonate and cooking treatment. Aspects of the invention are also receptive to pretreatment during the transport or storage of crushed fibrous material, for example as described in U.S. Patent 6,55,462, the disclosure of which is incorporated herein by reference. For batch systems, conventional means, such as pumping liquor into the vessel, may be used to displace the liquid in the digester, or the liquid may be discharged from the digester by the inherent pressure or pumping means prior to re-flow. Baking liquor be added in the digester. All liquids may be preheated using methods known in the art, such as liquor extracted from the SuperBatch or RDH methods. In addition, the liquid may be heated in the vessel through circulation circuits or by direct addition of steam.

As described herein, aspects of the present invention have a cellulosic material pretreatment process and a pulp production process that have advantageous improvements over prior art wood chip treatments, and related crushed cellulosic materials. As is clear from the test data presented here, pretreatment of wood chips with a carbonate solution, with or without the presence of anthraquinone, can produce cellulose pulp that has a higher yield, less tailings, higher strength and require fewer chemicals for both production and bleaching.

While various aspects of the present invention have been described and detailed herein, alternative aspects may be presented by those skilled in the art to achieve the same objectives. Accordingly, it is intended to cover all such alternative aspects by the appended claims, which fall within the spirit and true scope of the invention.

Claims (48)

Method of treating crushed cellulosic fibrous material, characterized in that it comprises: (a) treating the cellulosic fibrous material with a sulfur-free carbonate-containing solution to produce a pretreated cellulosic material; and b) treating the pretreated cellulosic material with a pulping chemical for a sufficient time and at a temperature sufficient to produce a cellulose pulp; wherein in at least one of a) and b) the cellulosic fibrous material is treated with an anthraquinone. Method according to claim 1, characterized in that the cellulosic fibrous material is treated with an anthraquinone in a). Method according to claim 1 or claim 2, characterized in that the pretreated cellulosic fibrous material is treated with an anthraquinone in b). Method according to any one of claims 1 to -3, characterized in that the carbonate-containing solution is composed of a sodium carbonate-containing solution. Method according to any one of claims 1 to -4, characterized in that the carbonate-containing solution is composed of an aqueous solution having a concentration of 1% to 12% carbonate as Na2O in the wood. Method according to Claim 5, characterized in that the concentration is composed of 3% to 9% carbonate as Na2O in wood. Method according to Claim 1, characterized in that the sulfur-free carbonate-containing solution is composed of a sulfur-free sodium carbonate solution. Method according to any one of claims 1 to 7, characterized in that the pulp production chemical is composed of sodium hydroxide. Method according to any one of claims 1 to 8, characterized in that the pulp production chemical consists of sodium hydroxide. Method according to any one of claims 1 to 9, characterized in that it is further composed, prior to the treatment of a), of c) treating the crushed fibrous material with an acidic solution. Method according to any one of claims 1 to 10, characterized in that it further comprises, after c) and before a), d) extracting at least part of the acid solution of the cellulosic fibrous material. Method according to Claim 4, characterized in that the sodium carbonate solution is composed of 1% to 12% sodium carbonate as Na2O in the chips. Method according to claim 12, characterized in that the sodium carbonate is composed of 2% to 7% sodium carbonate as Na2O in the chips. Method according to any one of Claims 1 to 13, characterized in that a) is practiced at a temperature greater than 100 ° C. Method according to any one of claims 1 to 14, characterized in that a) is practiced at a temperature between 120 ° C and 170 ° C. Method according to any one of claims 1 to 15, characterized in that a) is practiced at a temperature between 120 ° C and 150 ° C. Method according to any one of claims 1 to 16, characterized in that a) is practiced from 15 minutes to 120 minutes. Method according to any one of Claims 1 to 17, characterized in that it produces a pulp having a lower percentage of tailings and a higher percentage of sieving yield compared to a pulp produced by the method without the practice of a). Method according to any one of claims 1 to 18, characterized in that it is practiced continuously. A method according to any one of claims 1 to -19, further comprising an oxygen delignification treatment, and wherein the method produces a pulp having a lower kappa number after the oxygen delignification treatment in a predetermined sieve yield compared to a pulp produced by the method without the practice of a). Method according to any one of claims 1 to 20, characterized in that the treatment with anthraquinone is composed of an aqueous anthraquinone having a concentration between 0.01 wt% to 0.20 wt% relative to the chips. . A method according to any one of claims 1 to 21, characterized in that the anthraquinone treatment is composed of an aqueous anthraquinone having a concentration between 0.05 wt% to -0.10 wt% with respect to the chips. Method according to any one of claims 1-21, characterized in that the anthraquinone is introduced after a) and is composed of an aqueous anthraquinone concentration from 0.01 wt% to -0.20 wt% by weight. relation to splinters. A method according to any one of claims 1 to 23, characterized in that the treatment of the pretreated cellulosic material with a pulping chemical is further composed of the production of a liquid containing a spent pulping chemical. ; and where the method further comprises: treating the liquid containing the spent pulping chemical to produce a carbonate-containing solution from the spent pulping chemical; and utilizing the carbonate containing solution produced from the spent pulping chemical as the carbonate containing solution in a). Method according to claim 24, characterized in that the treatment of liquid containing the spent pulping chemical comprises: concentration of the liquid sufficient to withstand combustion; burning the concentrated liquid to produce a carbonate containing the melt; and introducing a liquid into the melt to produce the carbonate-containing solution from the spent pulp production chemical. A method according to claim 24 or claim 25, characterized in that the carbonate-containing solution is comprised of -2% to 7% sodium carbonate as Na2O relative to the chips. Pulp, characterized in that it is produced from the process as defined in any one of claims 1 to 26, wherein said pulp has a higher yield than pulp produced by the prior art. A method according to any of embodiments 1 to 26, further comprising an oxygen delignification treatment and at least one bleaching stage, wherein the method produces a cellulosic pulp having a clarity greater than 80 ° C. % elrepho. 29. Method of treating crushed cellulosic fibrous material, characterized in that it consists of: (a) treating the cellulosic fibrous material with an acidic solution; b) treating the cellulosic fibrous material with a carbonate-containing solution to produce a pretreated cellulosic material; and c) treating the pretreated cellulosic material with a sulfur-containing pulp producing chemical for a sufficient time and at a temperature sufficient to produce a cellulosic pulp; where in at least one of b) and c), the cellulosic fibrous material is treated with an anthraquinone. Method according to claim 29, characterized in that the cellulosic fibrous material is treated with an anthraquinone in b). A method according to claim 29 or claim 30, characterized in that the pretreated cellulosic fibrous material is treated with an anthraquinone in c). A method according to any one of claims 29 to 31, characterized in that the carbonate-containing solution is composed of a sodium carbonate-containing solution. A method according to any one of claims 29 to 32, characterized in that the solution containing sodium carbonate is composed of green kraft liquor. A method according to any one of claims -29 to 33, characterized in that the carbonate-containing solution is composed of an aqueous solution having a concentration of 1% to 12% of carbonate as Na2O relative to wood. A method according to any one of claims -29 to 34, characterized in that the carbonate-containing solution is composed of an aqueous solution having a concentration of 3% to 9% carbonate as Na2O relative to wood. A method according to any one of claims 29 to 35, characterized in that the method is further composed, after a) and before b), of d) extracting at least part of the acidic solution of the cellulosic fibrous material. A method according to any one of claims 29 to 36, characterized in that b) is practiced at a temperature greater than 100 ° C. A method according to any one of claims -29 to 37, characterized in that b) is practiced at a temperature between -120 ° C and 170 ° C. A method according to any one of claims -29 to 39, characterized in that b) is practiced at a temperature between -120 ° C and 150 ° C. Method according to any one of claims 29 to 40, characterized in that b) is practiced from 15 minutes to 120 minutes. Method according to any one of Claims -29 to 40, characterized in that the method produces a pulp having a lower tailings percentage and a higher sieved yield percentage compared to a pulp produced by the method without the use of b. ). Method according to any one of claims -29 to 41, characterized in that it is practiced continuously. A method according to any one of claims -29 to 42, further comprising an oxygen delignification treatment, and wherein the method produces a pulp having a lower kappa number after oxygen delignification treatment in a predetermined sieving yield compared to a pulp produced by the method without the use of b). A method according to any one of claims -29 to 43, characterized in that the anthraquinone treatment is comprised of a concentration between 0.01 wt% to 0.20 wt% relative to the chips. A method according to any one of claims 29 to 44, characterized in that the anthraquinone treatment is comprised of a concentration between 0.05 wt% to 0.10 wt% relative to the chips. Method according to any one of claims -29 to 45, characterized in that anthraquinone is introduced after b), and wherein the treatment with anthraquinone is comprised of a concentration between -0.01 wt% to 0.20% by weight in relation to the chips. A method according to any one of claims -29 to 46, characterized in that the treatment of the pretreated cellulosic material with a sulfur-containing pulping chemical is further composed of the production of a liquid containing the chemical-producing pulp. of spent pulp; and wherein the method further comprises: treating the liquid containing the pulp producing chemical to produce a carbonate containing solution from the spent pulping chemical; and the use of the carbonate containing solution produced from the spent pulping chemical as the carbonate containing solution in b). A method according to claim 47, characterized in that the treatment of the liquid containing the spent pulping chemical is composed of sufficient liquid concentration to withstand combustion; burning the concentrated liquid to produce a carbonate containing melt; and introducing a liquid into the melt to produce the carbonate-containing solution from the spent pulp production chemical.